Study On The Method Of Rapidly Detecting Lubricity By Using Dielectric Properties Of Diesel

In recent years,more and more attention has been paid to the problems of environmental pollution which were closely related to automobile exhaust emissions in our country.Compared with gasoline engine,diesel engine has the advantages of high efficiency,cleanness,energy saving and so on,therefore,regardless of from the environmental protection or the energy conservation point of view,the use of diesel oil will be greatly increased,the quality requirements of the diesel will be also getting higher and higher,sulfur content which has a significant impact on the environmental protection in diesel oil will be strictly controlled.But,with the promotion of low sulfur diesel,the rapid wear and tear of the components of the fuel pump system has been reported in most countries,that was due to lack of lubrication performance of low sulfur diesel.Adding lubricity additives to low sulfur diesel is the main method to improve the lubrication performance of low sulfur diesel.Lubricity additives are mainly polar compounds,which can improve the lubricity of diesel oil without affecting other properties,and they are economical,convenient and effective.At present,the domestic and foreign scholars have done a lot of research work on the detection methods of the lubricity of diesel oil,such as high frequency reciprocating rig method,four ball machine simulation evaluation method,full-size engine oil pump simulation experiment research and so on,but these methods generally require the test instruments relatively bulky and expensive,a long time,the test process is relatively complicated.Therefore,by extracting a small amount of polar heterocyclic compounds which have a greater contribution to the lubricity of diesel oil,and developing a new method for rapid detection of lubricity of diesel oil by dielectric property have great significance to guarantee the lubricity of diesel.Dielectric loss and dielectric constant are usually the main factors for the evaluation of dielectric properties,in addition,the capacitance value and resistivity.In this experiment,the hydrofining diesel oil which produced in refinery with no antiwear agent was selected as the research object.Its composition and dielectric properties were measured at different temperatures.The results show that the dielectric loss and dielectric constant of hydrofining diesel oil are small,and there is a certain regularity with the change of temperature.The dielectric loss is sensitive to the change of temperature,and increases exponentially with the increase of temperature;the resistivity is inversely proportional to the exponent and decreases with the increase of temperature;there is a good linear relationship between dielectric constant and temperature;at the same time,there is a good linear relationship between capacitance and temperature.In order to study the influence of the content of the anti-wear agent on the dielectric properties,the diesel oil samples with different anti-wear agents were prepared and their dielectric properties were measured,to explore the correlation between the two.The results show that the dielectric loss,dielectric constant and capacitance increase with the increase of the anti-wear agent,and the resistivity decreases.The content of anti-wear agent(0～100)mg/kg has little effect on the dielectric properties;the content of the anti-wear agent(100～450)mg/kg,the dielectric properties began to change dramatically.The dielectric loss,the capacitance value and the resistivity have no obvious regularity with the change of the anti-wear agent content,but the dielectric constant has a good correlation with the grinding agent content.Finally in order to study the relativity between diesel dielectric property and lubricity,determination of lubricity of samples with different concentrations of anti-wear agent(correction of grinding spot diameter),and its dielectric properties for fitting,the results show that the correlation between the dielectric constant and the grinding spot diameter is the best.By using formula model directly calculated value compared with measured value,the linear superposition is very good,so it can through measurement of diesel oil dielectric constant,used for diesel calibration grinding spot diameter measurement.At the same time,it provides a good basis for the further development of the method to detect the lubricity of diesel oil.